The chief of intelligence in the Israeli police saidpreventive arrests had been made to foil attacks on publicutilities.

"We have information, verified in recent days after wecarried out the arrests, that there is an intention to carryout attacks on infrastructure, and that is a very dangerousmatter," police Brigadier Yaacov Peleg told Israeli Army Radio.

Activists opposed to the Gaza pull-out were preparing toblock evening rush-hour traffic across Israel. In what appearedto be a related act of vandalism, spikes were scattered on ahighway during morning rush hour, slashing the tires of 20cars.

Prime Minister Ariel Sharon vowed on Tuesday to stamp out"wild behavior" of ultranationalists bent on scuttling his bidto stem 4 1/2 years of Israeli-Palestinian bloodshed byevacuating Gaza and a corner of the West Bank.

Rightists say Sharon's "Disengagement Plan" is a betrayalof Jewish claims on biblical land and a recipe for morePalestinian violence.

Representatives of the Jewish settlers slated forevacuation have called for passive protests only.

"We, of course, are opposed to all sorts of violence," saidEmily Amrusy, spokeswoman for Yesha, the umbrella settlercouncil. She described the spikes scattered on Route One nearIsrael's international airport as "an expression offrustration" by maverick ultranationalists.